Clot retrieval devices comprising a self-expanding Nitinol stent-like member disposed at the end of a long shaft are commonly used to remove clot from blood vessels, particularly from patients suffering from acute ischemic stroke. These devices are typically provided with small marker bands at either end of the self-expanding member which help to indicate the device's position. It would be very beneficial to a physician to be able to see the full expandable body of such a device under fluoroscopy, and thus receive visual information on the device's condition as rather than simply its position. Clot retrieval procedures are conducted under an x-ray field in order to allow the user visualise the anatomy and at a minimum the device position during a procedure. It is desirable, and enhances the user experience to be able to visualise the device state as well as position structure during a procedure, for example if the device is in an expanded configuration or a collapsed configuration. This means that the radopiaque sections must move closer to the device axis in a collapsed configuration and further from a device axis in an expanded configuration. It is generally desirable to make interventional devices such as clot retrieval devices more flexible and lower profile to improve deliverability in interventional procedures. This may be achieved by reducing the dimensions for device features, and the level of contrast seen under x-ray is generally reduced as the device dimensions are reduced. Radiopaque materials generally comprise noble metals such as gold, tantalum, tungsten, platinum, iridium and the like, and generally have poor elastic recovery from a strained condition and are therefore not optimal material for devices, particularly for the regions of these devices undergoing high strain in moving from a collapsed to an expanded state and vice versa. Radiopaque materials may be added through coating a structure comprising a highly recoverable elastic material such as Nitinol, but coating the entire structure has a dampening effect that inhibits device performance.
This invention overcomes limitations associated with the dampening effect of adding radiopaque material to an expandable clot retrieval device, while making the structure sufficiently radiopaque to allow full visualisation of the device condition as well as position.